Accelerator Pedal Position Sensor & Throttle Control Motor Don't Turn Together? - TTORA Forum
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Old 07-14-2005, 12:39 AM   #1
DennisDawg
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Angry Accelerator Pedal Position Sensor & Throttle Control Motor Don't Turn Together?

2003, Tacoma, V6, Auto, S/C, 7th and all that . . . I was driving down the freeway and every now and then it is like I took my foot off the gas Ė but I didnít! If I step on it, it is fine. I used to think my foot had just slipped sometimes! Very intermittent. It did it a few time months ago a lot but went away and then this past weekend, it did it every few minutes until it stuck that way. The truck still goes, can do freeway speeds, but there is considerable play in the gas petal and canít floor it (even when floored).

So I clean the throttle body and check everything. Still the same. I compare this to another Tacoma. If both are running and one grabs the throttle linkage at the Accelerator Pedal Position Sensor (front of Throttle Body) and turn it counter clockwise, a good V6 will rev with nearly zero play while mine twists about 15 degrees or more before anything happens, the same as the play in the petal.

Though it threw a Check Engine Light when throttle response went away it went out on its own before I could hook up the ODBII reader and get the code and has not come back.

So I start the diagnostics in the Toyota Manual (at SF-28). Linkage OK, with ignition on I can hear the Throttle Control Motor, The Throttle Opening Percentage goes to 60% but not much more, Idle is good . . . The Throttle Control Motorís motor resistance is in range but the clutch is 5.3 ohms (range is 4.2 to 5.2). However, the temp was above 68 degrees as they list for measurement for the above range to be valid. Both the Accelerator Pedal Position Sensor and the Throttle Position Sensor read in range and checking the other pins, they seem to change resistance smoothly (but I do not know if the ranges are right as I do not have a min and max resistance spec for the extremes of these potentiometers).

If I take the Accelerator Pedal Position Sensor off but leave it connected and the ignition turned on and turn the sensor, the Throttle Control Motor clutch does not immediately engage (but I can hear it click) and reflect the movements of the Accelerator Pedal Position Sensor. The 15 degree or so gap is there. If I move the Accelerator Pedal Position Sensor back and forth, there are times that the Throttle Body responds slowly as well.

So, is the Accelerator Pedal Position Sensor bad (increased potentiometer resistance) and not letting the ECU know I am stepping on the gas until it has moved. Is the Throttle Control Motor or its clutch failing? Anything else?
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Old 07-14-2005, 12:44 AM   #2
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Sounds like the Throttle Control Motor is going in and out of safe mode. In safe mode, the throttle output will be limited to certain amounts, regardless of how far you push the gas pedal.

Are you using a scan tool to read the codes?

This is probably something that needs to be looked at by a technician with a Toyota scan tool, i.e. at the dealership.
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Old 07-14-2005, 08:00 AM   #3
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There are a LOT of these throttle by wire throttle bodies on the 3.4 that are having problems all over the damn place. I get about 5 emails a week from people with some kind of drivability problem relating to these throttle body assemblies.

The sad thing is that none of the parts are available individually and if one part in that assembly goes bad the whole throttle body assembly needs to be replaced. I have seen them go from $600-1000.

That new throttle by wire assembly was installed on 2002 and later 4Runners, and 2003 and later Tacomas. At least you guys have that cable still on there that will allow you to force the throttle open about 20% if the system fails so you can pull out of the roadway. The 05 trucks do not. If it craps out you sit right there in everyones way.

Another piece of good news is that this throttle body is not covered under the power train warranty or so Toyota says. Once you drive out of the 3/36 bumper to bumper warranty and it craps out you are the one that has to suck up the replacement costs.

If people that end up having a failed throttle body assembly would keep filing complaints on the NHTSA website and describe how you feel this is a safety issue because it could fail when you are pulling out in front of that big dump truck in morning rush hour then maybe they will start an investigation and force a recall on it.

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Old 07-14-2005, 10:23 AM   #4
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I am using a laptop and OBDII tool to look at the beast. The only code it threw up was days ago, on the way to Las Vegas, when the failure became hard. I was still able to drive at Freeway sppeds (and higher) and cruise control worked fine. By the time we got to Las Vegas the code was gone and 600 miles later when I hooked up, there was nothing to read. I can see the Throttle Valve Opening Percentage and can get it over 60%.

It is the initial 15% or so play in the cable, where it is turning at the Accelerator Position Sensor but it is not contacting the throttle itself and opening it, and the Throttle Control Motor is not turning (just during that 15%). The mechanical gap is normal, but the lack of reaction is not. The Motor should turn immediately.

The mechanics are clean, no sand or dust inside.

I can find the Throttle Position Sensor for sale on line but the Accelerator Position Sensor and the Motor, I cannot find.

I hate going to the dealer . . . though my last time in was 100% fine . . . it takes a lot of time out form the day . . .

Iíd rather just fix it, if possible . . .
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Old 07-14-2005, 08:17 PM   #5
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I think it's the throttle control motor. Unless you can figure out what's wrong, which I doubt you can without a thorough understanding of the system's operation, you need to go to the dealership.

It's unfortunate that it takes a lot of time out of your day, but that's something your either going to have to deal with, or not. If you choose to not deal with it, this problem could persist for a long time.
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Old 07-14-2005, 09:01 PM   #6
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Mine does the same thing. I played with the wires a couple of months ago and it stopped for at least 2 months. It now just started doing it again. I think the problem is electric. I remember a while back Gadget on Custom Tacos saying something about his partner at URD Brian fixing the problem by improving the grounding on the TB.
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Old 07-14-2005, 11:05 PM   #7
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Quote:
Originally Posted by AK98Taco
I think it's the throttle control motor. Unless you can figure out what's wrong, which I doubt you can without a thorough understanding of the system's operation, you need to go to the dealership.
I have a really good understanding of how it works, but as Gadget pointed out, I may not have access to parts . . . and the dealership may be the only way to go. But, I am going to hold out for a bit for a solution either given or invented.
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Old 07-14-2005, 11:09 PM   #8
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Quote:
Originally Posted by citrustaco
Mine does the same thing. I played with the wires a couple of months ago and it stopped for at least 2 months. It now just started doing it again. I think the problem is electric. I remember a while back Gadget on Custom Tacos saying something about his partner at URD Brian fixing the problem by improving the grounding on the TB.
Hmmm, now that is something I did not consider, though during investigation I did notice that with everything not bolted in place, it did not work to well and I assumed that was the lack of proper ground, then thought no more of it. Perhaps you are onto something!!!

It would fit because it showed the symptoms initially many months ago, then stopped doing it for the most part until very recently. Component failure normally would not be such that it failed, then fixed itself for a long time and then failed again. So wiring and grounding are also likely culprits worth digging into!! Thanks!!!

Is this it? http://www.customtacos.com/ubbthread...=&fpart=4&vc=1

Last edited by DennisDawg; 07-14-2005 at 11:50 PM.
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Old 07-14-2005, 11:09 PM   #9
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If the motor fails, you won't have any solution but to replace it, at which point you can only get it from the dealership.

You can hold out all you want, but the dealership should be able to fix it in less time than it would take you.

Good luck to you!
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Old 07-14-2005, 11:28 PM   #10
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Quote:
Originally Posted by AK98Taco
If the motor fails, you won't have any solution but to replace it, at which point you can only get it from the dealership.

You can hold out all you want, but the dealership should be able to fix it in less time than it would take you.

Good luck to you!
Maybe . . . we'll see . . . and if I have to take it in, then I will but maybe I will not have to . . . I like to do things myself, learn . . . then I know for later . . .
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Old 07-17-2005, 08:22 PM   #11
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As it turns out the Accelerator Petal Position Sensor Assembly is the issue. This is the plastic assembly at the front on the Throttle Body to which the Accelerator Cable attaches. Though the 03 has a cable it is not intended to regularly directly control the throttle's position but rather it turns potentiometer that then changes a voltage that is applied to the ECU's electronics indicating the potion of the pedal. The ECU uses that data turn the Throttle Control Motor and engage its clutch, which actually opens and closes the throttle.

The throttle has a catch at 90 degrees into which an arm on the Accelerator Petal Position Sensor Assembly fits but this arm is at about 60 to 70 degrees, not contacting the throttle. This is normal. It is so that if there is a failure, one can still mechanically control the throttle somewhat.

The Accelerator Petal Position Sensor Assembly has a shaft onto which the lever for the accelerator cable is mounted with some return springs. This shaft also turns the potentiometer. This lever (a plastic piece) limits the travel of the assembly, so the highest and lowest resistances of the potentiometer are not encountered in the potentiometer.

The problem is that the potentiometer can also turn in the assembly, loosing its reference to the arm and lever. Then the range of resistance that is possible can be changed. If it turns too far one way, the higher resistance will be such that there is not sufficient voltage sent to the ECU to indicate that the pedal has been depressed. Conversely, there is a point at the other end of the petitioner where the full voltage is applied and the ECU sees this as a failure and closes the throttle by releasing the Throttle Control Motor's clutch. My case was the former.

By removing the Accelerator Petal Position Sensor Assembly, removing the springs and nut, and leaving it connected to the circuit with the ignition on, I could use the lever to turn the potentiometer to beyond its and reposition it. While doing so I was listening for when the Throttle Control Motor's clutch to engage to position the potentiometer so that occurred near the start (the stop to which the springs turn it) of the assembly's travel.

Now it runs fine. In fact the throttle response is the best it has been in a very long time. I believe that the potentiometer was likely moving a little bit occasionally over months and months and on the trip to Las Vegas it had moved to the point of becoming a real issue.

Will it continue to do so? I think it'll need a new Accelerator Petal Position Sensor Assembly all the same. find me one!!!!???

I also think the design of the Accelerator Petal Position Sensor Assembly is flawed. Carefully using an ohmmeter I could see positions in the potentiometer that may be questionable. This may be do to vibration wear or dirt and may cuase issue at some point. However, more important is the fact that the potentiometer's position is not secured well in the assembly. When I experienced loss of power is was always in the desert in rather hot air (105+). Could the increased temperatures cause expansion in the plastic and loosen it?

Anyway, that is where it stand today . . . seems to be good for now and I'll look into more after I get a few other tasks done, like find a new job! <G>
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Old 07-17-2005, 08:41 PM   #12
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Very interesting.

We have an older ('94) LS400 in the shop right now that is having a fuel cutoff problem. When under hard acceleration, power is cut off and the vehicle just lurches as the throttle goes on-off, on-off. We originally thought the problem was in the TPS, but after replacing it (for the second time in the vehicle's history), the problem still occurrs, though intermittently.

We now believe the problem to be in the ECM or the wiring between the sensor and the ECM.

It is common for potentiometer-type sensors like the TPS to gain a memory from constant driving at certain speeds. Over time, they will develop a node on that part of the sensor and lose contact.

I really hope you can figure out more on what the problem is with your particular truck. I will ask my parts people tomorrow to get a quote for a new APPS, just to give you an idea on what you would be getting into. I'll get the price for a customer purchase and the price with my discount. I will also ask some the better techs at the shop if they have any experience with problems like this.

Best of luck with this challenging problem!
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Old 07-17-2005, 10:06 PM   #13
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Quote:
Originally Posted by AK98Taco
. . . llurches as the throttle goes on-off, on-off. We originally thought the problem was in the TPS, but after replacing it (for the second time in the vehicle's history), the problem still occurrs, though intermittently.
Wiring could be it as could a bad potentiometer in your scenario. As you said, with vibration, they can develop what you called a node, a depression from wear or a build up of dirt or other substance in one spot. I thought it has to be a wiring issue for me because the low power issue would occur very intermittently, with months or minutes between occurrences.

In the 03 Tacoma, if one disconnects the APPS, the RMPs will go down for a bit and then race up to about 2K. I found this very odd as it could mean that at a place in the potentiometer where greater than 2K ohms were encountered might cause the engine seemingly bog then surge. I found this very odd as an issue with the APPS could be taken as something very different.


Quote:
Originally Posted by AK98Taco
I really hope you can figure out more on what the problem is with your particular truck.

I am 99% certain it is the potentiometer in the APPS rotating out of position a little bit at a time, over time. with it set up correctly now, the trucks throttle works like it did when new. However, I worry, though it is easy to fix, that it will rotate again. I know this should not rotate, but the abundance of plastic and glue leaves little to make it completely secure. When I get a new one, I'll open up this old one for fun and see what it really wrong in there.

Quote:
Originally Posted by AK98Taco
I will ask my parts people tomorrow to get a quote for a new APPS, just to give you an idea on what you would be getting into. I'll get the price for a customer purchase and the price with my discount. I will also ask some the better techs at the shop if they have any experience with problems like this.
Thank you!!! That will be very helpful and I hope that the information here will also be helpful to others, hence the nearly over documentation effort in regard to what I found. I look forward to your pricing information. I might get more than one APPS and a TPS just to put in the spares box - they seem to be the weak links in the Throttle Body.
It is running great now!!!
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Old 07-18-2005, 12:03 AM   #14
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You should make a write-up for the tech section. Your findings need to be saved.
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Old 07-18-2005, 09:50 AM   #15
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Quote:
Originally Posted by AK98Taco
You should make a write-up for the tech section. Your findings need to be saved.
I just might do that . . . thanks.
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Old 07-18-2005, 08:10 PM   #16
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I looked into the parts for you.

The parts guy couldn't find an Accelerator Pedal Position Sensor for the pre-'05s, but he found a TPS, which runs about $70.

My other parts people will be in tomorrow and I'll have them look as well.
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Old 07-18-2005, 08:44 PM   #17
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Quote:
Originally Posted by AK98Taco
You should make a write-up for the tech section. Your findings need to be saved.

I could not agree more. Please do one. I would love to learn something from it.


P.S. when will I stop being a newbie
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Old 08-08-2005, 03:07 PM   #18
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Quote:
Originally Posted by DennisDawg
2003, Tacoma, V6, Auto, S/C, 7th and all that . . . I was driving down the freeway and every now and then it is like I took my foot off the gas Ė but I didnít! If I step on it, it is fine. I used to think my foot had just slipped sometimes! Very intermittent. It did it a few time months ago a lot but went away and then this past weekend, it did it every few minutes until it stuck that way. The truck still goes, can do freeway speeds, but there is considerable play in the gas petal and canít floor it (even when floored).

So I clean the throttle body and check everything. Still the same. I compare this to another Tacoma. If both are running and one grabs the throttle linkage at the Accelerator Pedal Position Sensor (front of Throttle Body) and turn it counter clockwise, a good V6 will rev with nearly zero play while mine twists about 15 degrees or more before anything happens, the same as the play in the petal.

Though it threw a Check Engine Light when throttle response went away it went out on its own before I could hook up the ODBII reader and get the code and has not come back.

So I start the diagnostics in the Toyota Manual (at SF-28). Linkage OK, with ignition on I can hear the Throttle Control Motor, The Throttle Opening Percentage goes to 60% but not much more, Idle is good . . . The Throttle Control Motorís motor resistance is in range but the clutch is 5.3 ohms (range is 4.2 to 5.2). However, the temp was above 68 degrees as they list for measurement for the above range to be valid. Both the Accelerator Pedal Position Sensor and the Throttle Position Sensor read in range and checking the other pins, they seem to change resistance smoothly (but I do not know if the ranges are right as I do not have a min and max resistance spec for the extremes of these potentiometers).

If I take the Accelerator Pedal Position Sensor off but leave it connected and the ignition turned on and turn the sensor, the Throttle Control Motor clutch does not immediately engage (but I can hear it click) and reflect the movements of the Accelerator Pedal Position Sensor. The 15 degree or so gap is there. If I move the Accelerator Pedal Position Sensor back and forth, there are times that the Throttle Body responds slowly as well.

So, is the Accelerator Pedal Position Sensor bad (increased potentiometer resistance) and not letting the ECU know I am stepping on the gas until it has moved. Is the Throttle Control Motor or its clutch failing? Anything else?

Any news with this Dennis ? I think my truck might be doing the same thing. I have a 5 spd. Sometimes when I'm cruising at above and near 3K, in a little higher than normal gear, I noticed that for split second it feels like my foot slipped of the accelerator. I wear sandels a lot so I use to think it was my sandels but after reading your post, I may have a problem with my APPS.
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Old 08-08-2005, 03:29 PM   #19
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That is just what mine felt like. I blamed shoes and floor mats and would do all sorts of things to stop it, then it would stop for a while (months) before it finally got to be a hard failure . . and I was enjoying some quality under hood time in a hot, vacant lot in picturesque Baker, California. Ha ha!

Since the last time I looked at it, cleaned it up and adjusted it as best as I could, it has not been an issue. I have had it in the dirt and up on the freeway without issue. Maybe it is fixed.

The interesting thing is how much the Throttle Position Sensor (TPS) and Accelerator Petal Position Sensor (APPS) interact. In the electronics it would seem they are in the same circuit, so that if you move one, it impacts the other. For example adjusting the APPS to a position my correct the throttle cut out can change the idle speed, moving the TPS to correct for this will electronically change the position of the APPS, possibly to where the ECU it cuts it out. It is a balancing act. When you are all done, resetting the ECU can upset the whole balance again as the converted voltage level(s) are obviously stored and resetting brings them to the default, incompatible with the physical positions youíve set. Messing with it can cause you to spend a lot of time getting it back.

I have a new throttle body from which I was going to take resistance readings to see where a factory adjusted throttle bodyís TPS and APPS were adjusted. Then see if that matched with mine. I am sure that in the factory they put it on a test set and adjust the TPS position to meet some voltage or resistance level that matches it to the APPS.

It could be a bad spot in the APPS or TPS. To test these Iíd suggest not using a digital meter but one with a needle. Digital meters have a sampling rate and as you turn the sensor you hit the bad spot when the meter is not sampling, youíll not see it. regardless, go slow and see if the resistance climb or fall is linear for both sensors, without removing or repositioning them.
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Old 08-08-2005, 04:30 PM   #20
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There could be some mechanical slip in there somewhere, Dennis. Have you looked into the trottle body while moving the throttle? Could the TPS could be slipping on the shaft from the TB butterfly shaft? Yours is a later model than mine so I don't have the control motor. It's all mechanical.
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Old 08-08-2005, 05:11 PM   #21
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Quote:
Originally Posted by Dick Foster
There could be some mechanical slip in there somewhere, Dennis. Have you looked into the trottle body while moving the throttle? Could the TPS could be slipping on the shaft from the TB butterfly shaft? Yours is a later model than mine so I don't have the control motor. It's all mechanical.
I have looked at the throttle body opening and closing, engine on, engine off, had it all apart and back together . . . seen it all . . . taken it apart again . .. tested parts of it disassembled, disconnected and in so many ways it made me crazy! <G>



Mechanically, everything seems to have been working fine but for the APPS having rotated slightly out of position (as previously described).



In normal operation the 3.4L 2003ís are throttle by wire. I do not know if the TPS somehow not moving with the Throttle Postion Motor(slipping) could cause the same issue. The TPS is on the Throttle Position Motorís cover and physically tied to its clutch and gear system. Its position seems to greatly impact idle speed as well . . . I am not sure what would occur if it slipped up or down resistance while rolling along.



On my truck I do not feel it was the TPS that was the problem. The rheostat in the APPS had physically changed position in its mount. When the ECU becomes confused over APPS position, it tends to let the throttle close (in most cases not all).



After messing with it a while back (as previously described), I have been running it for a while now, freeway and dirt . . . no problems. In fact it is running better than it has in months!

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Old 08-08-2005, 05:47 PM   #22
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Quote:
Originally Posted by DennisDawg
After messing with it a while back (as previously described), I have been running it for a while now, freeway and dirt . . . no problems. In fact it is running better than it has in months!
Dennis, thank goodness you figured it out. The APPS is not available by itself, requires a new throttle body (~$675). I can only guess the reason Toyota offers the TPS (~$37) is because they don't want anyone f***g with the mechanical linkage.

Best thread in along time, thanks for your research!
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Old 08-08-2005, 11:14 PM   #23
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Quote:
Originally Posted by valkyrie
Dennis, thank goodness you figured it out. The APPS is not available by itself, requires a new throttle body (~$675). I can only guess the reason Toyota offers the TPS (~$37) is because they don't want anyone f***g with the mechanical linkage.

Best thread in along time, thanks for your research!
Thanks for the kind words.



I was told by a number of dealers that the APPS was not available. I wanted one as a spare. It is funny that they do not sell the APPS. It does not appear to be adjustable when it is in its correct configuration. It with the rest of the plastic cable connection and return springs are simply bolted in place as an assembly with four screws and no adjustment. On the other hand, the TPS is adjustable. Its position can be changed in that you can loosen two screws and rotate it to change its reference to the gears associated with the Throttle Control Motor. The ECU is very much impacted by its position. It will change the idle speed . . but if youíve it all wrong and reset the ECU, it will not recover correct idle speed.



It is a balance. When I get a few minutes Iíll take the good factory adjusted throttle body I have as a spare and put the meter on it to get the range the rheostats are mechanically limited to in their correct positions.



Anyway, my point was that it would seem that if a part is not adjustable, like the APPS, theyíd sell it more readily than the one that was, like the TPS. But it is the other way around. The APPS and TPS are both just rheostats, and I canít see why theyíd replace the entire throttle Body for a bad rheostat. A simple adjustment procedure is certainly done in the factory and could easily be done in the field.



The Toyota manual has one test only the continuity of the rheostatís track, not the wiperís ability to maintain contact with the track which is a common mode of failure and should also be checked. The wiper could be complete disconnected and the test they outline would not show a problem.
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Old 08-13-2005, 05:31 PM   #24
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Dennis,

Great news for you.I'm currently on a road trip in so cal and the problem has greatly increased. Sometimes this will happen at stoplight while acclerating from a full stop. I feel like I'm burning the clutch but the truck just dosen't go.

So did you just take the APPSA apart and some how it works great now?

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Originally Posted by DennisDawg

By removing the Accelerator Petal Position Sensor Assembly, removing the springs and nut, and leaving it connected to the circuit with the ignition on, I could use the lever to turn the potentiometer to beyond its and reposition it. While doing so I was listening for when the Throttle Control Motor's clutch to engage to position the potentiometer so that occurred near the start (the stop to which the springs turn it) of the assembly's travel.

Now it runs fine. In fact the throttle response is the best it has been in a very long time. I believe that the potentiometer was likely moving a little bit occasionally over months and months and on the trip to Las Vegas it had moved to the point of becoming a real issue.

Will it continue to do so? I think it'll need a new Accelerator Petal Position Sensor Assembly all the same. find me one!!!!???

I also think the design of the Accelerator Petal Position Sensor Assembly is flawed. Carefully using an ohmmeter I could see positions in the potentiometer that may be questionable. This may be do to vibration wear or dirt and may cuase issue at some point. However, more important is the fact that the potentiometer's position is not secured well in the assembly. When I experienced loss of power is was always in the desert in rather hot air (105+). Could the increased temperatures cause expansion in the plastic and loosen it?

Anyway, that is where it stand today . . . seems to be good for now and I'll look into more after I get a few other tasks done, like find a new job! <G>
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Old 08-16-2005, 10:40 PM   #25
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Hey Dennis,

I came across this thread and just a few days ago started having similar symptoms. At first I thought that I had left the truck in neutral after backing out of my driveway. Then I thought I was low on AT tranny fluid since I have seen this on cars with low fluid. But then I noticed that my RPM's weren't climbing when I step on the throttle. It's like a pause when you step on the throttle and is really annoying. I notice mine when my truck is cold like in the mornings but after it warms up it's fine.

I work for Honeywell and we manufacture variable resistance devices (potentiometers) and we have had field failures come back on our products for intermittent failures. Typically what happens is that there isn't enough dielectric grease on the resistive track and over time with heat and vibration the contact spring wears down along with the resistive ink applied to the substrate. Depending on how the mechanical stack up is between all of the components if the potentiometer has any endplay when rotated the contact spring (wiper) will lose contact with the resistive surface and cause intermittency.

When and if you change your sensor, if you send me your old one I can have my reliability lab do a failure analysis on it to determine the root cause. I'm approaching my 3yr/36K warranty so maybe mine will die soon and I can have it replaced by the stealership for free.

Robert
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Old 08-16-2005, 11:46 PM   #26
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Robert,

Have you looked at your sensor? In a way, I'm happy that you, Dennis and I are having the same problem because it means that I'm not going crazy and this truely a problem but on the other hand there isnt really a fix but makes .

On my drive up from so cal (warmer temp) to nor cal (warm temp) I didnt have any problems with my sensor cutting out. I don't know if the change in temp was really a factor though but I did unplug and plug the sensor just to check out the connection. On drive down I had cut out problem like 3 to 4 times each morning.

The most annoying and possibly danngerous (with a 5 sp at least) thing about this problem is that if you are waiting for a red light while at an incline, you'll stall the truck even though you press on the acclerator with more than normal pressure. It happend to me a couple times and I had to almost burn my clutch to get it go forward and not stall and roll backwards. Of course you can always step on the brakes to prevent bumping into the vehnicle behind you but its still very annoying.


Quote:
Originally Posted by LocoTaco
Hey Dennis,

I came across this thread and just a few days ago started having similar symptoms. At first I thought that I had left the truck in neutral after backing out of my driveway. Then I thought I was low on AT tranny fluid since I have seen this on cars with low fluid. But then I noticed that my RPM's weren't climbing when I step on the throttle. It's like a pause when you step on the throttle and is really annoying. I notice mine when my truck is cold like in the mornings but after it warms up it's fine.

I work for Honeywell and we manufacture variable resistance devices (potentiometers) and we have had field failures come back on our products for intermittent failures. Typically what happens is that there isn't enough dielectric grease on the resistive track and over time with heat and vibration the contact spring wears down along with the resistive ink applied to the substrate. Depending on how the mechanical stack up is between all of the components if the potentiometer has any endplay when rotated the contact spring (wiper) will lose contact with the resistive surface and cause intermittency.

When and if you change your sensor, if you send me your old one I can have my reliability lab do a failure analysis on it to determine the root cause. I'm approaching my 3yr/36K warranty so maybe mine will die soon and I can have it replaced by the stealership for free.

Robert
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Old 08-17-2005, 06:39 AM   #27
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Default I got the hesitation too.

Experience the same kinda things with my auto as well. Hit a certain throttle point or boost level hard to determine which one it is still. Sometimes right at boost or when going uphill. All sounds related to the same stuff. I can make it do it but try not of course. Had this for a good while now.

Sam
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Old 08-17-2005, 03:19 PM   #28
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Hello Jim,

I would imagine it is a pain in the ass with a 5-speed. Mine is pissing me off, because it's like your mind has been programmed for years that when you step on the gas you see a reaction either forward movement or RPM's increase. The symptoms are like there is a dead spot when you step on the pedal. I'm hoping mine starts to become worse so I can take it in. I bet there is more people out there with the same problem but have not come forward yet. Maybe we should start posting on that safety site like Gadget said so they start a recall.

Robert
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Old 08-17-2005, 04:46 PM   #29
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Robert, how did yours start? Since you have an auto I would imagine it is a slightly different feel than others. Mine hasn't started to do that I don't think. I do feel a slight pull back and tug every now and then when I am just coasting at highway speeds. I guess it could be considered a feeling you get when you let off the peddle and go right back to the same position. The only way I could describe it is a misfire of some sort, yet not a misfire(smoother and not as jerky). It doesn't happen all the time and it is very subtle. That is why I dismissed it. I have had so much axel wrap that at take off I would always dismiss hesitations like that to wheel hop. I installed my traction bar yesterday so no more blaming axel wrap, I have yet to feel it at take off. However, I could never quite attribute the highway speed issue to anything. Since it doesnít happen very often and is very subtle I never thought about it. Just wondering it that is what everyone means when they say ďnot as bad at first,Ē and I am experiencing the beginning of a bigger problem yet to come. Or like Jim mentioned I could be imagining it all and Iím just going crazy.

Jose
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Old 08-17-2005, 09:56 PM   #30
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Jose:

What you describe could be what we are experiencing. Mine started in the mornings when the truck is cold. At first it would go away within a mile but today I noticed it after driving it for more than 30 minutes. It always does it when I take off from a dead stop.

Robert
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